Circulators are three-terminal devices which pass signal inputs from one port to the next in a rotational fashion (either clockwise or counterclockwise) with allowing the signal inputs to pass in the opposite direction. Circulators are suitable for any radio frequency (RF) applications including communications, cell phones, radar, phased array radar and electronic countermeasures (ECM). A typical arrangement for a circulator is for the antenna to be designated as port 1, the receiver, port 2 and the transmitter as port 3. Thus, a signal from the antenna will travel to the receiver, a signal from the receiver to the transmitter and the transmitter to the antenna. Some of the transmitter signal will carry over to the receiver.
During transmission, the circulator isolates the sensitive receiver from the large transmitter signal. Since the received signal travels from the antenna to the receiver, it is isolated from the transmitter. The circulator causes a loss in the outgoing signal from the transmitter amplifier. This signal loss reduces the range at which radar can detect objects, or that a wireless device can communicate. On reception, the circulator also causes a loss in the receiver path. Because this loss is occurs before the low-noise amplifiers, the loss value adds to the noise value of the receiver path, degrading the magnitude of the minimal detection signal.
Circulators have a certain size and weight that is determined by the frequency of use. When the circulator is used in a spaced-base phased array application, the total weight of the circulator is large. Circulator architectures impart sacrifices to both output power and the noise figure. In general, circulators operate with high noise figures, low output signal levels, and are heavy with large profiles. These and other disadvantages are solved or reduced with using this new device.